What is the scale of the maps? if the scale is low, say 1:250,000 or lower, you could use a modern datum, since the errors won't make much of a difference.
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Devdatta TengsheMay 20 '13 at 4:14

Based on the years you gave, I'd bet that a datum wasn't even used. It was probably projected directly from an ellipsoid or spheroid. If you can figure out what projection the map is in, you might be able to derive the ellipsoid used and go from there.
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MintxMay 20 '13 at 21:14